JPS60182318A - Control device of variable displacement turbocharger - Google Patents

Abstract

PURPOSE:To reduce a decrease of torque in an engine in its high speed range even if the nozzle designed point of a variable displacement mechanism is suited to intermediate and low speed ranges, by driving a variable displacement mechanism and an exhaust-gas bypass mechanism by the supercharge pressure to be controlled in mutual relation to a speed of the engine and a flow of air. CONSTITUTION:A control means 21, using the supercharge pressure Pb as a driving pressure source for both a variable displacement mechanism 14 and an exhaust-gas bypass mechanism 15, inputs an engine speed Ne and an air flow Qa. In the range of a part C, a flap valve 23 of the variable displacement mechanism 14 increases its opening while a swing valve 41 of the exhaust-gas bypass mechanism 15 is left as closed. In a range D, the control means fully opens the flap valve, while opens the swing valve allowing exhaust gas to flow bypassing a turbine 12.

Description

[Detailed Description of the Invention] [Prior Art] Generally, a turbocharged engine rotates a turbine by using the energy of exhaust gas emitted by the engine.
The coaxial compressor is rotated to increase the amount of air entering the cylinder, which increases the compressor outlet pressure, i.e.
This is to obtain supercharging pressure (positive pressure higher than atmospheric pressure) and to improve engine output (torque) and fuel efficiency.

In this case, the boost pressure cannot be increased unnecessarily in order to prevent damage to the engine, so an exhaust bypass mechanism is provided to bypass the turbine and reduce the flow rate of the exhaust gas flowing into the turbine.

On the other hand, boost pressure, which is related to engine output, is uniquely determined by the turbine capacity, so using a small flow turbine improves engine torque at low speeds, but reduces torque at high speeds. Conversely, if a high-flow turbine is used, the torque at high speeds will improve, but the torque at low and medium speeds will decrease. Therefore, a variable displacement turbocharger has been proposed that can increase the engine torque from low speed range to high speed range by changing the capacity of the turbine according to the operating state of the engine (Utility Model Application No. 53-50310). (see official bulletin).

This conventional variable prefecture turbocharger changes the exhaust flow rate to the turbine by changing the area of the scroll inlet of the turbine housing or the area of the movable part of the nozzle ring surrounding the turbine, thereby controlling the compressor outlet pressure to a predetermined level. It is possible to maintain boost pressure and increase torque from a constant speed range to a high speed range.

However, when applying such a conventional variable displacement turbocharger to a high-speed automobile engine where the flow range is several times larger between low and high engine speeds and controlling boost pressure, it is difficult to control the boost pressure over the entire operating range. (This ensures good turbine efficiency.) It becomes difficult to control the exhaust gas, which has a flow rate several times higher, using only the variable mechanism, and for this reason, a combination with an exhaust bypass mechanism is absolutely necessary. In that case, simply combining the two mechanisms will result in both mechanisms moving in relation to each other with respect to the same engine exhaust pressure.
If this happens, the other one will close and move in conjunction with the other, making it impossible to obtain proper boost pressure. In other words, if you try to increase boost pressure in the low engine speed range by closing the variable displacement mechanism, i.e. by reducing the flow rate characteristics, the exhaust passage will be constricted, resulting in an extremely high engine exhaust pressure and exhaust bypass. There is a problem in that the valve opens and the supercharging pressure does not rise against the request, making it impossible to obtain 1 herk. Due to the differences in the mechanisms (such as There was a problem in that the engine torque deteriorated and it was difficult to improve the torque by 1 to 100 mph over the entire engine rotation range.

[Object of the Invention] This invention has been made by focusing on the problems of the conventional J. Even in the area where the control area and the control area of the exhaust bypass mechanism overlap, the supercharging pressure is prevented from sagging, and even if the variable displacement mechanism malfunctions, the supercharging pressure does not rise excessively and is further variable. It is an object of the present invention to provide a control device for a variable displacement turbocharger that smoothly changes supercharging pressure regardless of changes in operating conditions from a displacement mechanism operating range to an exhaust bypass mechanism operating range.

[Configuration of the Invention] 3- In order to achieve the above object, the present invention comprises: a variable displacement mechanism that changes the flow rate characteristics of a turbine; an exhaust bypass mechanism that causes engine exhaust gas to flow bypassing the turbine; and the variable displacement mechanism. A variable displacement mechanism driving means for driving the exhaust bypass mechanism using engine boost pressure as a driving source, and control for controlling the exhaust bypass mechanism driving means in relation to each other with respect to engine rotation speed and air flow rate. The gist is that the means have been established.

[Function] The variable displacement mechanism and the exhaust bypass mechanism are controlled in relation to each other by the engine speed and the air flow rate using the supercharging pressure as the driving source, so that a predetermined supercharging pressure is obtained in each region. ] - Maximum torque in each range can be obtained by the variable displacement mechanism in the engine low and medium speed ranges and by the exhaust bypass mechanism in the high speed range.

The present invention will be explained below based on the drawings.

1 to 5 are diagrams showing an embodiment of the present invention.

4-First, the engine 1 whose overall configuration is shown in FIG.
(4) is measured by an aflow meter 5, and a predetermined amount of fuel is injected and supplied by an intake manifold 4.

The exhaust gas that has finished working within the engine 1 is eventually exhausted through an exhaust manifold 6 and an exhaust pipe 7.

The turbocharger 11 is connected to the turbine 12 and the compressor 1
A turbine 12, housed in an exhaust manifold 6, is rotated by the energy of the exhaust gas and rotates a compressor 13 housed in the intake pipe 2, thereby pressurizing intake air to obtain supercharging pressure pb.

The turbocharger 11 has an exhaust inlet section (the first section).
A variable displacement mechanism 14 is provided in the exhaust manifold 6.
An exhaust bypass mechanism 15 is provided in a bypass passage 8 that connects the exhaust pipe 7 and the exhaust pipe 7.

Both the variable capacity mechanism 14 and the exhaust bypass mechanism 15 are connected to pipes 16 and 1 so that the pressure of the supercharging pressure Pb is used as a driving source.
7, and receives a signal of the engine speed No. from the crank angle sensor (rotation speed detection means) 9, and detects the air flow fM.
It is wired to a control means 21 which receives and processes the Qa signal from the air flow meter 5.

Figure 2 shows the specific structure for controlling both mechanisms.

A flap valve 23 is installed at the turbine inlet and is connected to a diaphragm 26 of an actuator 25 by a link 24. The diaphragm 26 is biased by a spring 27 so as to oppose the supercharging pressure pb introduced from the pipe 26. .Piping 1
A solenoid valve 29 is connected to the relief conduit 28 and a relief conduit 28 is connected downstream of the conduit 6, and the other end is connected to the -L flow of the compressor 13 downstream of the air flow meter 5. is provided, and the duty control of A-off is performed by the command from the control means 21.

As shown in FIG. 3, the flap valve 23 is located at the exhaust inlet portion 32 of the spiral scroll 31, and swings about a shaft 33 to change the area of the exhaust inlet portion 32, that is, the throat area. The shaft 33 is connected to the aforementioned link 24 by a lever 34.

Referring again to FIG. 2, a swing valve 41 is provided in the exhaust bypass passage 8 so as to cover the outlet and is connected to a diaphragm 714 of the actuator 43 via a link 42. The diaphragm 44 is guided here by a spring 45. The piping 17 is provided with a throttle 46, and a relief conduit 47 is connected downstream of the conduit 46, the other end of which is connected to the aforementioned relief conduit 28. A solenoid valve 48 is installed (duty control is performed by the control means 21).

The intake pipe 2 is provided with a relief valve 49 for emergency measures, and a throttle valve opening sensor 50 for detecting the position of the throttle valve 3 is also provided.

Further, a knock sensor 51 is attached to the main body of the engine 1 to detect knocking when it occurs.

The control means 21 is usually configured as a control unit, and mainly has a microcomputer consisting of a microprocessor, memory, and an interface. Signals from the corner sensor 9 and knock sensor 51 are input.

The analog signal behind these signals is input as a digital signal via an A/D converter. Memory stores programs that control the microprocessor and various data necessary for operations performed by the microprocessor, and
Data imported from outside is also temporarily stored. The microprocessor executes fuel injection DAm according to the above program.
, calculates the injection timing, ignition timing, etc., and outputs the injection signal @S and the ignition signal Sp appropriate for the cone engine operating condition.

Furthermore, the control means 21 controls the solenoid valve 29 of the variable displacement mechanism 14.
The microprocessor calculates duty values suitable for the solenoid valves 48 of the exhaust bypass mechanism 15, respectively, and outputs them as a signal DM and a signal Dw from the interface.

Next, the operation of the embodiment will be explained based on the flowchart shown in FIG.

The control calculation in this embodiment is executed, for example, once per revolution or once every fixed period of time. When the program starts, the JOB execution order is determined by JOB control, and then the calculation routine for the variable displacement mechanism and the calculation routine for the exhaust bypass mechanism are respectively executed.

(1) Calculation routine of variable capacity mechanism The left side (a) of FIG. 4 is a Ji calculation job, and P represents each step of the program flow. First, the engine speed No. and the A/D conversion value of the air flow mQa are input at Pl, and P
2, the air flow rate Tp per engine rotation is calculated by 4.

In P3, engine rotation speed Ne and air flow rate per rotation T
A predetermined duty value for p is looked up from the table on the right.

Since this table has a finite number of division points between NO and Tp,
A proportional interpolation calculation is performed on the numerical values between the dividing points, and the basic duty value DM is determined.

Furthermore, in P4, the basic duty value D that is looked up is
It is determined whether M is between the upper limit value Du- and the lower limit D+-. This is to deal with the activation delay time of the solenoid valve and the malfunction of the software part, and to eliminate both extreme values (near DutV 100% and 0%). in this case,
If DM is a predetermined value, it is output to Pr, but if it is larger than D, DM is fixed at the upper limit value at P5, and when it is smaller than DL, it is output to Pr.
Fix M to the lower limit. Then, the basic duty value looked up by Pr is stored in the memory, and a timer measurement unit (not shown) calculates the duty to the solenoid valve according to the value in the memory, and the result is sent to the solenoid valve via the I10 interface. is sent to the solenoid valve 29 (
The operation of FIG. 2) is determined.

(2) Estimated calculation routine for exhaust bypass mechanism In the calculation job shown on the right side (b) of FIG. 4, P represents each step of the program flow.

First, in P8, the engine speed Ne and the air flow rate Qa are A/
A D conversion value is input. At part D, the air flow rate Tp per engine rotation is calculated. Pr.

Then, a predetermined duty value for the engine speed and the air flow rate per revolution Tp is looked up from the table on the right.

Since this table has a finite number of division points between NO and Tp,
Proportional interpolation 81 calculation is performed on the numerical values between the division points, and the basic duty value DvJM is determined.

Further, in Pl+, the basic duty value DwM that is looked up is - the limit value Dvvw and the lower limit value II) w1. −
Determine whether there is a difference between the two. This is to deal with the activation delay time of the solenoid valve and the malfunction of the calculation software section, and to eliminate both extreme values. In this case, DWv
If is a predetermined value, it is output to P+4, but when it is larger than DWw, P+2rDWv is fixed to the upper limit value, and when it is smaller than DW+-, it is output to P+4.
3 fixes the DWM to the lower limit value. Then, the basic duty value DWM looked up at P+4 is stored in the memory, and the duty to the solenoid valve is calculated in a timer measurement section (not shown) according to the value in this memory, and the result is 1.
10 interface to the solenoid valve, which determines the operation of the solenoid valve 48 (FIG. 2). In this embodiment, the -C1 table lookup is performed for the engine rotation and the air flow rate per revolution, but for the exhaust bypass mechanism, the table lookup is performed only for the air flow rate. Good too.

This is because the air flow value generally changes by about 100 times at maximum rotation speed with the throttle fully open compared to at low load (idle) due to engine load, rotation, etc.
Very high A/D conversion accuracy is required for microcomputers, etc., so when the air flow rate changes are large, a table is given using the air flow rate per revolution.
In cases where the operating range is narrow, such as an exhaust bypass valve, it is better to provide a table for the air flow rate, since the duty value will change almost correspondingly to the air flow rate, which will reduce reading errors when looking up the table. This is because it can be made smaller.

(3) Practical control Next, the actual control will be explained with reference to FIGS. 2 and 5.

First, in Fig. 5, if the horizontal axis represents the engine rotation speed 12-NO and the vertical axis represents the air flow ff1Tp per rotation, the operating line with the throttle valve fully open becomes line E, and the flap valve of the variable displacement mechanism The point where the supercharging pressure Pb reaches the specified value, for example 375 mm of mercury column, is the 81- line when the is closed, and the Bu line is the point where the boost pressure Pb reaches the specified value when fully open. ) is a region where the opening degree changes, and the opening operation is performed in the direction of the arrow.

Further, the exhaust bypass mechanism operates in a region between the dotted line A line and the full-open operation line F line, which are determined before and after the 3u line (in front in the figure).

The above-mentioned 0 part table and D part table are prepared separately, and at that time, the boost pressure Pb is set at full rotation so that it reaches the maximum boost pressure allowed in terms of engine characteristics, durability, and reliability. The control value is determined in advance in the area.

Now, assuming that a certain operating state is denoted by F, the opening degree of the flap valve is determined by the 0-part table, and the variable displacement mechanism is activated.

That is, the decoding value DM is determined from the flowchart 1 to (a) in FIG. 4, and the solenoid valve 29 in FIG.
5 is released to the relief conduit 28 and weakened. In this case, as the duty value decreases, the off time becomes longer, the amount of relief of the solenoid valve 29 decreases, and the opening degree of the flap valve 23 increases via the link 24.

As a result, the opening degree of the flap valve increases from point F in the direction of the arrow, and the capacity increases. In this 0 part region, the table of the exhaust bypass mechanism 15 has a duty value at which the solenoid valve 48 is opened, and the spring 45
The swing valve 41 remains on the closed side due to the relationship with the spring constant. Therefore, the turbocharger 11 obtains the maximum supercharging pressure Pb in the operating state with a predetermined exhaust flow rate without wasting exhaust energy, so the engine 1 exerts maximum torque in that state.

or<l, T, I) and reaches point G, for example,
Next, the duty value DWM is determined from the flowchart of FIG. 4(b), and a command is issued to the solenoid valve 48. At the same time, a command is given to the electromagnetic valve 29 with a duty value at which the flap valve 23 is fully opened. As a result, the swing valve 41 is similarly opened as the duty value decreases, so the exhaust bypass mechanism 15 bypasses the exhaust gas to the turbine 12 and operates at the supercharging pressure pb. Subtract 1q from the maximum allowable value in the state.

Even at point J: G, the engine 1 is operated at the maximum boost pressure and generates the maximum torque in that state. Moreover, the supercharging pressure does not become excessive, which prevents problems such as engine damage.

If necessary, in the lap range of both areas C and D, the variable capacity flap valve should be at its maximum opening within the range that can provide 1q of predetermined boost pressure, and the exhaust bypass swing valve should be fully open or closed to its maximum extent. In other words, the control values (duty value) of both tables and both driving means are set so that the opening operation start pressure of the swing valve 41 is slightly higher than the boost pressure value determined by the opening degree setting value (duty value) of the flap valve. Determine the spring constant, orifice, etc. In this way, when the engine accelerates, etc., the C area 15
- When shifting to the D region, it is possible to prevent the occurrence of a level difference in the control boost pressure due to variations in each component of both drive means or errors in setting.

In the above embodiment, the supercharging pressure Pb is used as the pressure source for the actuator, so even if this changes for some reason, for example if pb rises above a predetermined value, the flap valve 23 is Or, since the swing valve 41 is opened, the supercharging pressure pb is lowered, and
In the opposite case, the supercharging pressure is increased, thus achieving the effect of constantly maintaining a predetermined supercharging pressure.

Furthermore, if the duty value for controlling the solenoid valve 48 is kept within a predetermined range (avoiding a fully open or completely open state), and if the spring constant of the spring 45 is appropriately selected, the operating range of the variable displacement mechanism can be adjusted. Even if the flap valve malfunctions, as described above, the swing valve 41 opens as the supercharging pressure increases, thereby preventing the supercharging pressure from increasing.

FIG. 6 shows a flowchart according to another embodiment.

16- This embodiment aims to improve acceleration performance by increasing the supercharging pressure Pb above the steady value during engine acceleration regardless of the operating range of the variable displacement mechanism or the operating range of the exhaust bypass mechanism. .

That is, in FIG. 6, the engine speed is input at P+, and the throttle valve position from the throttle valve opening sensor 50 (FIG. 2) is input at P2. After determining the acceleration state in P3, the variable displacement mechanism duty correction mA that will increase the boost pressure by a specified amount during acceleration is read from the one-dimensional table in P4, and similarly, the exhaust bypass mechanism is adjusted in P5. Read the duty correction amount B from the one-dimensional table. If it is steady, the modified MA and B are decreased by k per unit time in P6 and finally decreased to 0.

This is to prevent sudden torque fluctuations from occurring when the vehicle changes from acceleration to steady running.

P7 and P8 perform a table lookup and correction calculation for the variable displacement mechanism duty and the exhaust bypass mechanism duty, and this routine is repeated thereafter.

For example, P7 is a program similar to the previous embodiment, as shown in detail at the bottom of FIG.
The difference is that is reduced by the correction amount A.

Furthermore, FIG. 7 shows a flowchart according to another embodiment.

This means that even if knocking occurs during acceleration, that is, when the boost pressure is increased further than the steady state, the correction amount A or B is kept constant per unit time as in the case of steady state. The value is decreased by ik and smoothly returned to the table value.

That is, 1) In step 1, a knock detection signal from the knock sensor 951 (Fig. 2) is input.This signal is determined by a known knock detection circuit used in conventional turbocharged engines. Also, at P'3, Pa
Even if it is determined that acceleration is occurring as a result of the acceleration determination, if a knock occurs due to the knock determination, the correction amount A is set at P6 as in the steady state.
Alternatively, B is decreased, and only when there is no knock, the supercharging correction amount A or B is looked up.

In the latter case, the flow goes to the routines P4 and P5, and in the former case, the flow goes to the routines Py and Pa, and the same operation as in the previous embodiment is performed.

[Effects of the Invention] As explained above, according to the present invention, the configuration uses a variable displacement mechanism and an exhaust bypass mechanism, each mechanism is driven by supercharging pressure, and the engine speed and air flow rate are controlled. Because the configurations are controlled in relation to each other, even if the nozzle design point of the variable displacement mechanism is set to suit the low and medium speed range, the drop in torque in the high speed range can be minimized, and the variable displacement It is possible to prevent the supercharging pressure from entering the operating range of the mechanism, and it is possible to achieve the effect of improving torque in the entire engine rotation range.

In addition to the above-mentioned effects, each of the embodiments also has the following effects.

That is, supercharging is possible during acceleration, and the rise in supercharging pressure is finely and reliably controlled, resulting in a noticeable improvement in acceleration.

Furthermore, even if knock occurs during acceleration, supercharging is avoided by the knock sensor, so it is possible to improve the torque during acceleration within a safer and more reliable range.

Note that vacuum pressure may be used instead of supercharging pressure as the power source for the actuators of both mechanisms, and in that case, a signal of supercharging pressure shall be input to the control means.

Further, although a signal from a crank angle sensor is used for the engine rotation speed, an ignition pulse may be used instead of this, or a vehicle speed signal from the vehicle speed side may be used instead.

Further, the air flow rate may be the air flow rate per engine rotation, or may be a signal of the engine load such as the opening degree of the throttle valve.

[Brief explanation of drawings]

FIG. 1 is an overall diagram of the present invention, FIG. 2 is a diagram showing a specific embodiment of FIG. 1, and FIG. 3 is a sectional view of the main part of the variable capacity mechanism.
FIG. 4 is a flowchart of an embodiment of the control program;
FIG. 5 is a table explanatory diagram, and FIGS. 6 and 7 are flowcharts of other embodiments of the control program. 20- Explanation of symbols appearing in the drawings 1... Engine 2... Intake pipe 3... Throttle valve 4... Intake manifold 5)... Air 70- Meter 6... Exhaust manifold 7. ...Exhaust pipe 8...Bypass passage 9...Crank angle sensor (engine speed detection means) 11...Turbocharger 12...Turbine 13...Compressor 14...
・Variable capacity mechanism 15...Exhaust bypass mechanism

Claims (1)

[Claims] a variable displacement mechanism that changes the flow rate characteristics of the turbine; an exhaust bypass mechanism that causes engine exhaust gas to bypass the turbine; and a variable displacement mechanism that drives the variable displacement mechanism and the exhaust bypass mechanism using engine boost pressure as a driving source. A control device for a variable displacement turbocharger, comprising mechanism drive means, exhaust bypass mechanism drive means, and control means for controlling the drive means in relation to each other with respect to engine speed and air flow rate.